"The probability that intelligent life which eventually attempts interstellar communication will evolve in a star system is usually expressed by the :p = f_pn_ef_lf_if_cwhere f_p is the probability that a given star system will have planets, n_e is the number of habitable planets in a solar system, f_l is the probability that life evolves on a habitable planet, f_i is the probability that intelligent life evolves on a planet with life, and f_c is the probability that an intelligent species will attempt interstellar communication within 5 billion years after the formation of the planet..."
Frank Jennings Tipler is an American mathematical physicist and cosmologist, holding a joint appointment in the Departments of Mathematics and Physics at Tulane University. Tipler has written books and papers on the Omega Point based on Pierre Teilhard de Chardin's religious ideas, which he claims is a mechanism for the resurrection of the dead. He is also known for his theories on the Tipler cyli
"What one needs is a self-reproducing universal constructor... a machine capable of making any device... capable of making a copy of itself. Von Neumann has shown... that such... is theoretically possible, and... a human being is a universal constructor specialized to perform on the surface of the Earth."
"I shall assume that such a species will... develop a self-replicating universal constructor with intelligence comparable to the human level—such a machine should be developed within a century, according to the experts...—and... combined with present-day rocket technology would make it possible to explore and/or colonize the Galaxy in less than 300 million years, for an initial investment less than the cost of operating a 10 MW microwave beacon for several hundred years, as proposed by SETI..."
"[I]t seems likely that a species engaging in interstellar communication would possess a fairly sophisticated computer technology. ...Sagan has asserted that Communication with extraterrestrial intelligence... will require... computer actuated machines with abilities approaching... intelligence."
"The basic idea... is straightforward and... has led other authors, such as Fermi... Dyson... Hart... Simpson... and Kuiper & Morris... to conclude that extraterrestrial beings do not exist: if they did exist and possessed the technology for interstellar communication, they would also have developed interstellar travel and thus would already be present in our solar system."
"[T]hus... any intelligent species would develop at least the rocket technology capable of... a travel velocity ves of 3 x 10-4c. At this velocity the travel time to the nearest stars would be between 104 and 105 years. This... would necessitate... self-repair capacity... Nuclear power-souces would supply the power... If power utilization during the free-fall period was... low, even chemical reactions could supply the power."
"As the copies of the space probe were made, they would be launched at the stars nearest the target star. When these probes reached these stars, the process would be repeated... until the probes covered all the stars of the Galaxy."